Lab - Eye And Ear

MCW 215 – Eye, Monkey iris

eyelid

lens Fovea (indentation)

Ciliary processes cornea

Ciliary body

Muscle of orbicularis oculi (palpebral part) Meibomian glands

MCO 0046 cornea Anterior compartment

Lens “shattered” from histological preparation

Vitreous compartment

Optic nerve

iris

Ciliary body

There are five distinguishable corneal layers. (p. 91) Various notes: -Bowman’s membrane is the basement membrane of the anterior epithelial layer. -Descemet’s membrane is the basement membrane of the endothelium. -Lamina propria - thickest layer (90% of the cornea) consists of regularly arranged lamellae of collagen fibrils (type I collagen), fibrocytes, and amorphous ground substance (mostly keratin and chondroitin sulfates).

Epithelium (outermost; stratified squamous)

Bowman’s membrane Lamina propria Descemet’s membrane

Endothelium (simple squamous)

Iris layers Anterior limiting layer

stroma Pigmented layer

Anterior limiting layer - Anterior surface of the iris covered with fenestrated layer of fibroblasts Stromal layer – middle region containing pigmented cells Posterior epithelium – layer of highly pigmented epithelial cells (p. 91)

Iris (low mag)

Sphincter pupillae muscle

MCW215

Ciliary processes Zonules of Zinn (attach to the suspensory ligaments of the lens)

NOTE: cilary body runs around circumference of eye (like iris)

Ciliary body – blood vessels in here produce aqueous humor that is actively transported into the posterior chamber

-aqueous humor circulates in the anterior chamber and is drained by channels near the junction of cornea, iris, and sclera (junction called iridio-corneal angle) -These channels drain into the canal of Schlemm and ultimately into scleral veins (p. 90)

cornea

Canal of Schlemm

iris

sclera

ciliary body

MCW 215

Sclera

Retinal layer

Choroid (has a heavy pigmented layer to absorb scattered light

MCO 0046

Sclera Retinal layer

Choroid

Cell bodies (nuclei) of photoreceptors

Photoreceptors extend these 3 layers

(1) Retinal pigmented epithelium (RPE)

Retina – 10 layers (6) Inner nuclear layer (2) photoreceptor layer

2 layers may not be well seen: (layer 3) - external limiting membrane (layer 10) -internal limiting membrane Muller cells (support cells analogous to glial cells) attached to the above two layers

NOTE: “inner” and “outer” named w/ respect to eyeball

(9) Optic nerve fiber layer

(8) Ganglion cell layer

(7) Inner plexiform layer

(5) Outer plexiform layer

(4) Outer nucelar layer

NOTE: cannot tell difference between rods and cones in routine histological stains

Retinal layers (p. 92) • Retinal pigmented epithelium (RPE) • Photoreceptor layer – light-staining; consists of outer and inner segments of rod and cone cells • External limiting membrane – thin layer that may be difficult to see; found at external ends of Muller cells (supporting cells of retina) where they form tight junctions between themselves as they encircle the photoreceptors. • Outer nuclear layer – has nuclei of rods and cones • Outer plexiform layer – light-staining layer; where photoreceptors synapse with dendrites of bipolar cells and horizontal cells • Inner nuclear layer – dark staining; has nuclei of (i) horizontal cells, (ii) bipolar cells, (iii) amacrine cells, and (iv) Muller cells • Inner plexiform layer – light staining; has synapses between amacrine cells and retinal ganglion cells • Ganglion cell layer – has retinal ganglion cell bodies • Optic nerve fiber layer – light staining; has axons of ganglion cells (that leave and synapse with CNS) • Internal limiting membrane – composed of basement membrane of Muller cells at its junction with the vitreous body

1 2 3 4 5 6 7 8 9 10

Fovea centralis – ganglion cells thin out

Lens – p. 92

External capsule of lens (type IV collagen) Epithelium (cuboidal) of lens

Lens fibers

iris

Optic Nerve Head – MCO 0122

Retinal layers

MCW 216 - cochlea The large spiraling channel of the cochlea is subdivided into three parallel canals (or scala) by the walls of the membranous labyrinth. Each of these channels contains fluid. a) Scala vestibuli (contains perilymph) b) Scala tympani (contains perilymph) c) Scala media (bounded by walls of membranous labyrinth – contains endolymph) p. 93-4

Modiolus – the central bony axis that the channels spirals around

Scala vestibuli

Osseous spiral lamina (medial attachment of scala media)

Reisner’s membrane (boundary between scala vestibuli and scala media)

Scala media (a.k.a. cochlear duct)

Spiral ligament (peripheral attachment of scala media to osseous labyrinth)

Spiral ganglion – cells

Basilar membrane

Scala tympani

Organ of Corti

Stria vascularis – vascular epithelium that produces endolymph; overlies lateral wall of scala media (cochlear duct) –p. 94

Basilar membrane

Spiral ganglion cells – situated within the modiolus

Reissner’s Membrane Stria vascularis Scala Vestibuli

Scala Media

Scala Tympani

Basilar Membrane

Organ of Corti

Tectorial membrane – where tips of hair cells are embedded (may be artifactually bent away from hair cells)

The sensory hair cells (inner one row; outer three rows) are embedded among the phalangeal cells

1 hair cell nucleus (inner)

-p. 94 3 nuclei of hair cells (outer)

3 nuclei of phalangeal cells NOTE: The inner hair cells are closest to the modiolus

Tunnel of Corti

Pillar cell (form walls of tunnel of Corti)

MCW 217 – crista ampullaris

Crista ampullaris (see next slide)

Crista ampullaris – the raised transverse ridge of the ampulla of each semicircular duct

Cupula (gelatinous glycoprotein) – where apical surface of the sensory hair cells insert

Hair cells and support cells (cannot distinguish the two here)

Axons of Scarpa’s ganglion entering

Crista ampullaris (NOTE: flipped compared to other slide)

Hair cells and support cells